1. Field of the Invention
The present invention relates to a controller constituting a semiconductor manufacturing apparatus, as well as a control method.
2. Description of the Related Art
Control accuracy of semiconductor manufacturing apparatuses is an important factor in the production of semiconductor wafers. Here, “control accuracy” refers to the margin of error in the time interval cycles in which, for example, opening/closing of a valve is controlled. For example, a control that was implemented in 50-ms cycles using a Microsoft Windows® operating system produced an error of approx. 50 ms±20 ms in terms of instructions actually output.
To reduce this error, a software program called “RTX” (real time extension) by Ardence can be incorporated into a Windows® operating system. When the two are combined, the error deceases to approx. 50 ms±1 ms.
However, RTX is an expensive product (costing approx. 5,000,000 yen), and therefore using it inevitably adds to the apparatus cost. Also, even when the cycle error of the operating system is reduced to ±1 ms, the inability to synchronize with the clock of the input/output control interface that receives the applicable instructions still results in an error of approx. ±1 ms. Consequently, there is always an error of 50 ms±2 or 3 ms.
In recent years, however, the trend for finer processing of semiconductor wafers is requiring that semiconductor manufacturing apparatuses be controlled in a manner not producing even 2 or 3 ms of error.